Cooling turbine rotors



Aug-16,1949 W.K; BODGER v 2,479,056

COOLING TURBINE ROTORS Filed Aug. 23, '1944 I 2 Sheets-Sheet l FIG.

ov v a"; Q -n m lNVENTOR 1949- v w. K. BODGER 2,479,056

COOLING TURBINE ROTORS Filed Aug. 23, 1944 2 Sheets-Sheet 2 3 5 Q U D 4co 5/ O XN D \x 3 2 7 a 4 Z N 6 Z s l. 2 w 9 0 9! g a 8 pg a INVENTORLUMMW Patented Aug. 16, 1949 UNITED STATES COOLING TURBINE ROTORS WalterKenneth Bodgcr, South Glastonbury, Conn., assignor to United AircraftCorporation, East Hartford, Conn., a corporation of Delaware ApplicationAugust 23, 1944, Serial No. 550,871

1 Claim. 1

This invention relates to cooling a rotor, particularly in a turbineadapted for operation by hot gases.

The oopending application of Ledwith, Serial No. 550,887, filed August23, 1944, describes a rotor having an axial bore through which a tubeextends for admitting fluid from one end of the rotor to coolingchambers adjacent the bearings at both ends. This arrangement permitsthe admission of fluid at the center of the rotor to avoid the action ofcentrifugal force on the fluid being pumped into the rotor. This tubealso prevents excessive heating of the fluid as it passes through thepower section of the rotor. A feature of the present invention is analternative construction in which the coolant tube is omitted.

When the rotor is built up of disks carrying blades and end sectionsheld together by a centrally extending through bolt the rotor has asubstantial axial expansion when in operation which applies a highstress'to the bolt. Since the allowable bolt stress is reduced as thetemperature of the bolt increases the bolt may become too hot towithstand the stresses resulting from the rotor expansion. A feature ofthis invention is an arrangement for internally cooling the bolt'for itsentire length.

Another feature is the cooling of both the bolt and the ends oftheturbine rotor by circulating coolant through the bolt from one endthrough chambers in the rotor adjacent the bearings.

The copending application of Soderberg and Kalitinsky, Serial No.550,885, filed August '23, 1944, discloses an arrangement for coolingthe disks of a built-up turbine rotor and for simultaneously cooling theconnecting bolt. ',A feature of this invention is the combination ofinternal bolt cooling with external cooling of this char acter formaintaining the bolt at such a temperature that the allowable boltstress will not be exceeded during turbine operation. v

Other objects and advantages will be apparent from the specification andclaim and from the accompanying drawings which illustrate an embodimentof the invention. I

Fig. l is a sectional view through the turbine.

Fig. 2 is a fragmentary sectional view on a. larger scale through thecentral bolt and the end sections of the turbine rotor.

The turbine shown includes a casting l built up of rings l2, l4, l6 andI8 and supported by radial pins 20 in a housing 22, These pins which areall in the same plane and which constitute the support for the casingwithin the housing engage bores in bosses 24 in one ring IQ of the 65around each disk thereby reducing the tempera.-v

2 casing. Rotor 26 within the casing has a number of rows of blades 28alternating with the rows of nozzles 3Bon the casings.

Housing 22 has a cap 34 which forms a part of the housing and supports abearing sleeve 38 for the front end of rotor 26. At the other end of theturbine the housing 22 supports a mounting 38 within which is a bearing40 for the rear end of the rotor. Mounting 38 has a number of legs 42engaging with radial pins 48 which support the mounting within thehousing.

Rotor 26 is made up of a number of disks 46, 48, '50 and 52, andshaft-forming end elements 55 and 56. The disks and the shaft elementsare all held together by a central bolt 58. The ends of the bolt arepositioned within the end elements 54 and 56 and are connected to theseelements by threaded sleeves 60 and 62. Each sleeve 60, t2 hasinner andouter threads 64 and 66 engaging respectively with cooperating threadson the bolt and on the end elements. On one of the sleeves (sleeve sq asshown) the inner and outer threads may differ in pitch, the inner threadbeing of 25 greater pitch, so that as the sleeve is screwed into place asubstantial tension may be applied to-the bolt. I

To assist in aligning the disks during assembly and to prevent relativerotation in operation each 30 disk has projecting annular flanges onopposite v sides, these flanges having elements preferably in the formoi.v face splines with similar elements on the adjoining disk.Similarly, the inner ends of shaft elements 54 and 56 have face splinesengaging with splines on the end disk.

Gas enters the first stage nozzles of the turbine through an inletscroll attached to the end of casing Ill. Gas from the turbinedischarges through a duct 72 connected to the end casing o ring andsurrounding the rear bearing mounting.

The disks which make up the power section of the rotor have centralopenings 18 slightly larger in diameter than the fastening bolt and theshaft elements 54 and 56 have central openings 80 and -82 also larger indiameter than the fastening bolt. The disks and shaft elements of therotor are thus free to expand radially without affecting the arrangementof the parts.

The rotor disks and the outside of the central bolt may be cooled byadmitting gas under pressure througha passage 88 in the front endelement to the opening between this element and the first disk 46. Gasfrom this space passes through the central openings in the disk and 3ture of the central parts of the disk and also reducing the temperatureof the bolt.

Coolant is admitted to the rearward end of the central bolt through atube 90 mounted in one of the projecting legs 42 of the bearing mounting30 and connecting with a passage 92 in bearing 40. A cap 94 on thebearing mounting has a connecting passage '96 by which coolant fromrpassage 92 is guided to'a tube 90 extending through a cap I on the endof the bolt. Since coolant enters at the axis of the bolt there are nocentrifugal forces acting on the fluid, as a result of the rotation ofthe rotor, until the fluid'reaches the bolt.

The bolt-has passages I02 adjacent its rearward and which communicatewith opening 82 permitting coolant to flow through this opening anddischarge through grooves I04 in the end element 56 to the inside of cap94.

Similarly, at the forward end of the bolt, passages I06 permit coolantto flow into the space 80 within the end element 54. Packing I08surrounding the bolt and located by a projecting rib IIO on the boltlimits the flow of coolant to the portion of space 80 forward of thepassages 88. Coolant in opening 80 discharges through ports H2 in endelement 54 and ports H4 in a journal II6 mounted on the end element.

As shown in Figure 2, packing I08 and similar packing II8 within endelement 56 may be held in place by sleeves I20 and I22 integral withsleeves 60 and 62 respectively. These sleeves have ports I24 and I26 topermit the flow of coolant from the inside of the sleeve to the outside.Since coolant is continually admitted to the rearward end of the boltand flows over the inner surface of the bolt for its entire length, thecentral bolt may be cooled to the desired temperature necessary forwithstanding the stresses applied to the bolt. At the same time, thepassage through the bolt directs fluid into the cooling spacessurrounding the bolt adjacent the bearings at opposite ends of therotor. A cap I28 closes the forward end of the rotor.

Under certain extreme conditions it is possible that the turbine mighthave to operate at approximately full power without opportunity tor theturbine to be heated gradually to the operating temperature. In thisevent, the rotor disks will be rapidly heated while the bolt remainspractically cold and the disk expansion will place a high axial load onthe bolt. If the bolt is to be sufliciently strong to withstand thisload it may be necessary to make the bolt of a material which, althoughcapable of being heat treated to high strength, loses its strengthrapidly at high To maintain the necessary high strength in the bolt thedirect cooling of the bolt both internally and externally may benecessary to prevent the bolt from reaching a temperature at which thebolt strength would be less than the temperature.

stress applied to it.

It is to be understood that the invention is not limited to the specificembodiment herein illustrated and described, but may be used in otherways without departure from its spirit as defined by the followingclaim.

I claim:

A turbine rotor having blade carrying disks having central openings andend shaft forming elements, a hollow axial bolt extending through saiddisks and elements and holding them together, each element forming achamber surrounding said bolt adjacent each end, means for admittingcoolant to said bolt, and means for admitting coolant from the bolt tosaid chambers, in combination with means for circulating another coolantbetween said bolt and the disks, the

latter having their central openings larger than the bolt to provide forthe circulation of the other coolant.

WALTER KENNETH BODGER.

REFERENCES CITED file of this patent:

UNITED STATES PATENTS The following references are of record in the

